The problem of ensuring that pits have been removed from cherries has long been a priority for the cherry producing industry. Over 95 percent of the tart cherry crop is pitted and processed into canned, frozen and dried fruit, or made into juice. In accordance with United States Department of Agriculture procedures, pitted cherries are separated into grades. Grade A cherries may not contain more than one pit per 2.5 pounds of finished cherries. Thus, it follows that if cherries are determined to be "Grade A" the producer has a more valuable product which commands a higher price. In addition, producer liability for impure products has recently become an issue given the potential for broken teeth, etc. when served as part of a meal in a pie, topping and the like. For the foregoing reasons, the cherry producers have set a goal of not more than one pit per 62.4 pounds of finished product.
In an effort to produce a finished cherry product with fewer pits, a number of devices have been produced which inspect the cherry after it has allegedly been pitted in an attempt to ensure pit removal. U.S. Pat. No. 4,666,045 to Gillespie et al. discloses one such apparatus and a method for detecting pits in cherries. Specifically, the patent teaches an optical pit detecting device comprising an inspection zone and a scanning beam generator that sweeps a transmission scanning beam across the inspection zone. An array of sensors are positioned on the opposite side of the inspection zone and produce a series of sensor signals that are proportional to the received light intensity based on the amount of light transmitted through the cherry. A second sizing beam generator generates a signal representative of the optical path length through which the transmission scanning beam travels within the fruit and generates a signal that is proportional to the size of the fruit. The two signals are then analyzed to determine the presence or absence of a pit within the fruit.
Another method and apparatus for detecting pits in fruit was disclosed in U.S. Pat. No. 5,077,477 to Stroman et al. The device comprised a U-shaped "inspection zone" in which a first side includes a linear array of infrared light emitting diodes and an adjacent linear array of infrared light sensors. Similarly, the opposite side of the inspection zone includes an array of sensors and an adjacent array of infrared light transmitting diodes that are adapted to receive/send signal from the opposite side of the inspection zone. Also provided for each of the foregoing is means for collimating the emitted light as well as a filter for reducing the ambient and scattered light on each of the sensors. The foregoing take the form of an aperture which has a smaller diameter than the size of the corresponding sensor/emitter. The apparatus measures both the transmitted and reflected light and utilizes an algorithm based on both of the foregoing to determine the presence or absence of a pit or pit fragment. This apparatus is not preferred since the diode characteristics shift relative to each other over time which degrades performance and frequent calibration is therefore required.
The potential methods as well as what is believed to be the state of the art for detecting pits in cherries is thoroughly discussed in the article entitled "Potential Methods for Detecting Pits in Tart Cherries" by E. J. Timm et al, which appeared in the January 1991 issue of Applied Engineering in Agriculture (Vol. 7(1) at pages 103-109) published by the American Society of Agricultural Engineers, S. Joseph, Mich. 49085-9659. The reader is referred thereto for an in depth discussion of the current state of the art of detecting pits in cherries.
To date, none of the known pit detectors have been widely adopted. It is believed that this is due to a number of factors including fruit deformation, high equipment cost, unacceptable error rates, machine speeds that are uneconomical and frequent detector down time due to component failure or the necessity for cleaning.
In view of the foregoing, it is therefore an object of the present invention to provide an improved method and apparatus for the detection of pits that meets or exceeds the industry set goal of not more than one pit per 62.4 pounds of cherries.
Another object of the present invention is to provide an improved method and apparatus for the detection of pits that permits non-destructive inspection and thus does not deform the fruit.
Another object of the present invention is to provide an improved method and apparatus for the detection of pits that is reliable.
Yet another object of the present invention is to provide an improved method and apparatus for the detection of pits that inspects the product at a high rate of speed.
Still another object of the present invention is to provide an improved method and apparatus for the detection of pits that is economical.